@article{fdi:010071370,
  title = {{C}hronological constraints on tsavorite mineralizations and related metamorphic episodes in southeast {K}enya},
  author = {{M}artelat, {J}. {E}. and {P}aquette, {J}. {L}. and {B}osse, {V}. and {G}iuliani, {G}aston and {M}onie, {P}. and {O}mito, {E}. and {S}imonet, {C}. and {O}hnenstetter, {D}. and {I}chan{G}'{I}, {D}. and {N}yamai, {C}. and {W}amunyu, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}savorite is exclusively hosted in the {N}eoproterozoic {M}etamorphic {M}ozambique {B}elt ({NMMB}). {T}he gemstone mines, widespread between {K}alalani ({T}anzania) and {M}gama {R}idge ({K}enya), define a continuous corridor over a hundred kilometers in length. {T}he tsavorite is hosted by a metasedimentary sequence defined as the {K}urase tsavorite-bearing metasediments ({K}urase{TB} metasediments) that also hosts rubies. {T}hese metasediments underwent amphibolite-facies metamorphism and are surrounded by granulitic gneisses that are also of sedimentary origin (the {K}urase high-temperature gneisses). {A}ll these rocks lie below the {K}asigau {G}roup, a unit dominated by granulite-facies metamagmatic rocks. {T}o constrain the timing of events that led to this peculiar occurrence of tsavorite, we have performed geochronological analyses of thin sections and of separated grains of zircon, monazite, and rutile using {LA}-{ICP}-{MS} and {ID}-{TIMS}, as well as 40 {A}r/ 39 {A}r of muscovite and phlogopite from various lithologies. {T}he results show that the different terranes were metamorphosed synchronously between 620-580 {M}a but under different {P}-{T} strain conditions. {T}he {K}urase-{HT} gneisses and the rocks from the {K}asigau {G}roup are highly strained and underwent granulite-facies metamorphism with abundant partial melting and emplacement of felsic melts between 620 and 600 {M}a. {T}extural observations also underlined a late regional water flux controlling the occurrence of {V}-free muscovite and monazite mineralizations at 585 {M}a. {T}he latter event can be related to theactivity of the {G}alana shear zone, in the east. {T}he {K}urase-{TB} metasediments escaped strain and partial melting. {T}hey record amphibolite-facies conditions with static heating, since initial sedimentary structures were locally preserved. {T}he age of the tsavorite mineralization was inferred at 600 {M}a from metamorphic zircon rims and monazite from the closest host-rocks, sampled in the mines. {H}ence, tsavorite crystallization occurred statically at the end of the metamorphic event, probably when the temperature and the amount of volatiles were at maximum levels. {C}onversely, the ruby formed by local metasomatism of felsic dikes and isolated ultramafic bodies. {T}he rubies are older and zircons and monazites from a ruby-bearing felsic dike (plumasite) were dated at 615 {M}a. {F}inally, data from rutile and micas indicate a global cooling below 430 degrees {C} of the whole region between 510 and 500 {M}a.},
  keywords = {tsavorite ; zircon and monazite in situ dating ; {A}r-{A}r dating ; {K}enya ; {T}savo ; granulite and amphibolite facies ; {KENYA}},
  booktitle = {},
  journal = {{C}anadian {M}ineralogist},
  volume = {55},
  numero = {5},
  pages = {845--865},
  ISSN = {0008-4476},
  year = {2017},
  DOI = {10.3749/canmin.1700019},
  URL = {https://www.documentation.ird.fr/hor/fdi:010071370},
}